Magnetic tape head system method specifying parameters for near-constant resolution at varying tape velocities

ABSTRACT

A magnetic tape head system and associated method are disclosed. Included is one or more head assemblies each including a base with a row bar coupled thereto with a head situated therein for defining a tape bearing surface defining a tape wrap angle with respect to a horizontal plane. A length of the tape bearing surface is between approximately 0.57 millimeters and 0.7 millimeters and the tape wrap angle is between approximately 0.5 degrees and 1.3 degrees such that a resolution of the magnetic tape head system is substantially independent of a velocity of the tape.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/255,858, filed Sep. 26, 2002 now U.S. Pat. No. 7,193,813.

FIELD OF THE INVENTION

The present invention relates to magnetic recording heads, and moreparticularly, this invention relates to flat profile tape recordingheads.

BACKGROUND OF THE INVENTION

Prior Art FIG. 1 illustrates a traditional flat-lapped bi-directional,two-module magnetic tape head 100, in accordance with the prior art. Asshown, a pair of bases 102 is equipped with row bars 104 each includinga substrate 104A and a closure 104B with readers and writers 106situated therebetween. In use, a tape 108 is moved over the row bars 104along a tape bearing surface 109 in the manner shown for reading andwriting data on the tape 108 using the readers and writers 106.Conventionally, a partial vacuum is formed between the tape 108 and thetape bearing surface 109 for maintaining the tape 108 in communicationwith the readers and writers 106. More information regarding suchflat-lapped magnetic tape head may be found with reference to U.S. Pat.No. 5,905,613, which is incorporated herein by reference.

Two common parameters are associated with heads of such design. Oneparameter includes the tape wrap angle 110 defined between a horizontalplane and a plane 111 in which the upper surface of the tape bearingsurface 109 resides. It should be noted that the tape wrap angle 110includes an internal wrap angle which is often similar in degree to anexternal wrap angle 115. Moreover, a tape bearing surface length 112 isdefined as the distance (in the direction of tape travel) between edgesof the tape bearing surface 109. Such parameters are often adjusted todeal with various operational aspects of heads such as that of Prior ArtFIG. 1, in a manner that will soon become apparent.

During use of the head FIG. 1, various effects traditionally occur.Prior Art FIG. 2A is an enlarged view of the area encircled in FIG. 1that illustrates a first known effect associated with the use of thehead 100 of FIG. 1. As shown, tents 202 form in the tape 108 on oppositeedges of the tape bearing surface 109.

Prior Art FIG. 2B is a cross-sectional view of the head 100 of FIG. 1taken along the illustrated line of FIG. 2A. As shown, tape lifting 204occurs along side edges of the tape bearing surface 109 as a result ofair leaking in at the edges and tape mechanical effects. Liftingadversely affects the end portions of the readers and writers 106. Stillyet, the tape lifting 204 results in additional stress at points 206which, in turn, causes additional wear. Further augmenting such tapelifting 204 is the fact that the tape 108 naturally has upturned edgesdue to widespread use of technology applied in the video tape arts.

During the design of the tape heads like that of FIG. 1, the tapebearing surface length 112 and tape wrap angle 110 may be varied tominimize the impact of some of the foregoing effects. For example, it isdesirable that the tape bearing surface length 112 be elongated in orderto reduce interaction of the aforementioned tents 202, which may, inturn, significantly reduce the proper communication between the tape 108and the readers and writers 106. Moreover, wear of the edges of the tapebearing surface 109 may result in shortening of the tape bearing surfacelength 112 over time. Thus, if the tape bearing surface length 112 is,at one time, sufficient to reduce the foregoing interaction, theshortening of the tape bearing surface length 112 may prompt suchinteraction over time. On the other hand, it is also desirable that thetape bearing surface length 112 be shortened to reduce theaforementioned lifting at the tape edges set forth during reference toFIG. 2B.

With respect to the tape wrap angle 110, there is a desire to increasesuch angle to combat the “edge loss” affect associated with the tapelifting 204 of FIG. 2B. On the other hand, there is a desire to minimizesuch tape wrap angle 110 to minimize the lateral extent (length in thedirection of the tape motion) of the tents 202 of FIG. 2A.

The balancing of the foregoing aspects has resulted in the design oftape heads 100 with a tape bearing surface length 112 of approximately0.8 mm, and a tape wrap angle 110 of approximately 1.8 degrees.

Recently, studies have shown that high frequency output of traditionalflat-lapped bi-directional, two-module magnetic tape heads, with certaintapes, can vary with tape speed. In particular, increasing tape speed ofthose tapes causes an increase in fly height, and thus a decrease inhigh frequency output. Still yet, this effect is lessened with continueduse of that particular tape sample. FIG. 2C illustrates such arelationship between the resolution (i.e. ratio of high frequency to lowfrequency output) of the tape head 100 and a velocity of the tape 108.While this effect is obscured to a small extent with many media, it isparticularly pronounced for other media.

Thus, as tape speed increases, resolution decreases because of thiseffect. Changes in resolution generally require changes in readequalization to keep error rates low, especially for partial responsemaximum likelihood (PRML) channels. This means that in applicationsrequiring “speed matching” in which drive speed varies in response touser-attached system speed, error rates may change with tape speed. Itis common goal that error rates be maintained at lowest possible levelsunder all operating conditions.

The origin of this effect (fly height or resolution vs. speed) is notfully understood. There has been a suggestion that it is related toviscoelastic stiffening of certain tapes as speed increases. There isthus a need for a head that addresses this problem of certain tapes, andgives a substantial improvement.

Fundamentally, the relationship shown in FIG. 2C appears to be a wrapangle-controlled effect. At larger tape wrap angles, the speed effect ismore pronounced than at lower wrap angles with the affected tapes.

As mentioned earlier, tape “tents” form on each edge of a head. See FIG.2A. The greater the wrap angle, the higher and longer the tent. Modelingand experiments have shown that at any tape speed larger tents tend tosuck more air into the head-tape interface and thus results in anincrease in head-tape separation in the region of the recording head.

For given geometrical wrap angles, stiffer tapes will have larger tents.If the tape appears dynamically stiffer as speed increases due toviscoelasticity, larger tents and a greater fly height may result. Inany case, shallow wrap angles give lower and less speed dependent flyheights.

Most tapes are manufactured with “cupping,” which is the tendency forthe tape surface to be convex when viewed from the magnetic coatingside. This property, which is needed for helical scan applications toprevent the heads from knicking the tape edges, coupled with anticlasticbending and side air leakage, tends to make the edges curl away from theflat head surfaces. This is particularly a concern when there are servotracks near the edges of the tape, such as with Linear Tape Open (LTO)standard tapes. Increasing the tape wrap angle tends to “straighten” thewrapping and generally reduce edge lifting, but this has the negativeeffect already described hereinabove.

DISCLOSURE OF THE INVENTION

A magnetic tape head system and associated method are disclosed.Included is one or more head assemblies each including a base with a rowbar coupled thereto with a head situated therein for defining a tapebearing surface over which a tape is adapted to pass during use of themagnetic tape head system.

In one embodiment, a length of the tape bearing surface may be selectedsuch that a resolution of the magnetic tape head system is substantiallyindependent of a velocity of the tape. Such tape bearing surface lengthmay be defined as a distance between edges of the tape bearing surface,along a direction in which the tape moves. As an option, the length ofthe tape bearing surface may be selected to be between approximately0.57 millimeters and 0.7 millimeters. Still yet, the length of the tapebearing surface may be selected to be substantially 0.63 millimeters.

The present embodiment solves the problems of the prior art byshortening the tape bearing length in the direction of tape travel. Ashorter length makes a given wrap angle more effective at straighteningwith respect to the curl, as the head tends to behave more like asmaller radius cylinder.

In another embodiment, a tape wrap angle may be defined by the tapebearing surface. In particular, the tape wrap angle may be defined by ahorizontal plane and a plane in which the tape bearing surface resides.As an option, the tape wrap angle may be selected to be betweenapproximately 0.5 degrees and 1.3 degrees. Moreover, the tape wrap anglemay be selected to be between approximately 0.8 degrees and 0.9 degrees.

Also provided is a magnetic tape drive for use with a magnetic recordingtape. Included is a tape drive system for moving the magnetic recordingtape linearly and bidirectionally. Associated therewith is one or morehead assemblies each including a base with a row bar coupled theretowith a head situated therein for defining a tape bearing surface which,in turn, defines a tape wrap angle with respect to a horizontal plane. Alength of the tape bearing surface is selected to be betweenapproximately 0.57 millimeters and 0.7 millimeters and the tape wrapangle is selected to be between approximately 0.5 degrees and 1.3degrees. Further included is at least one outrigger for defining anangle in which the tape approaches the head.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings.

Prior Art FIG. 1 illustrates a traditional flat-lapped magnetic tapehead, in accordance with the prior art.

Prior Art FIG. 2A is an enlarged view of the area encircled in FIG. 1that illustrates a first known effect associated with the use of thehead of FIG. 1.

Prior Art FIG. 2B is a cross-sectional view of a magnetic tape headtaken along the illustrated line of FIG. 2A, showing a second knowneffect associated with the use of the head of FIG. 1.

FIG. 2C illustrates a relationship between a resolution of a magnetictape head and a velocity of an associated tape.

FIG. 3 illustrates a flat-lapped magnetic tape head system, inaccordance with one embodiment.

FIG. 4 illustrates a tape drive which may be employed with the tape headsystem of FIG. 3 for one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.

FIG. 3 illustrates a flat-lapped magnetic tape head system 300, inaccordance with one embodiment. As shown, a pair of head assemblies 301is provided each with a base 302 that is equipped with a row bar 304each including a substrate and a closure with a reader/writer head 306situated therebetween. The row bar 304 and the base 302 may beintegrally coupled as a unitary unit or include two separate componentscoupled together. In the context of the present description, the row bar304 may include any portion of the head assemblies 301 to which the head306 is attached.

A tape 308 is moved along a tape bearing surface 309 in the manner shownfor reading and writing data on the tape 308 using the reader/writerhead 306. While a pair of head assemblies 301 is set forth herein, itshould be noted that one or more head assemblies 301 (i.e. 1, 3, etc.)may be provided per the desires of the user.

In use, a partial vacuum is formed between the tape 308 and the tapebearing surface 309. Such partial vacuum works to maintain the tape 308in communication with the reader/writer head 306. More informationreading the manufacture, operation, and use of such a flat-lappedmagnetic tape head may be found with reference to U.S. Pat. No.5,905,613, which is incorporated herein by reference.

To lessen the undesired relationship between a resolution of themagnetic tape head system 300 and a velocity of the tape 308 (See FIG.2C), various parameters such as the tape wrap angle (i.e. internal wrapangle) 310 and the tape bearing surface length 312 may be adjusted. Itshould be noted that, in one embodiment, the tape wrap angle 310includes an internal wrap angle which is often similar in degree to anexternal wrap angle 315.

In one embodiment, a length of the tape bearing surface 309 may beselected such that the resolution of the magnetic tape head system 300is substantially independent of the velocity of the tape 308. Such tapebearing surface length 312 may be defined as a distance between edges ofthe tape bearing surface 309, along a direction in which the tape 308moves. As an option, the length of the tape bearing surface 309 may beselected to be between approximately 0.57 millimeters and 0.7millimeters. Still yet, the length of the tape bearing surface 309 maybe selected to be substantially 0.63 millimeters. It should be notedthat these lengths are set forth for illustrative purposes, and anydesired lengths may be employed which are capable of reducing theundesired relationship between the resolution of the magnetic tape headsystem 300 and the velocity of the tape 108.

In another embodiment a tape wrap angle 310 may be defined by the tapebearing surface. In particular, the tape wrap angle 310 may be definedby a horizontal plane and a plane 311 in which the tape bearing surface309 resides. As an option, the tape wrap angle 310 may be selected to bebetween approximately 0.5 degrees and 1.3 degrees. Moreover, the tapewrap angle 310 may be selected to be between approximately 0.8 degreesand 0.9 degrees. Again, it should be noted that these angles 310 are setforth for illustrative purposes, and any desired angles 310 may beemployed which are capable of reducing the undesired relationshipbetween a resolution of the magnetic tape head system 300 and a velocityof the tape 108.

As an option, a pair of outriggers 314 may be used for defining an anglein which the tape 308 approaches the head 306. As yet another option, adistance between end edges of the row bars 304 may be selected to bebetween approximately 0.6 millimeters and 0.8 millimeters.

With the foregoing parameters adjusted in the abovementioned manner, theundesired relationship between the resolution of the magnetic tape headsystem 300 and the velocity of the tape 108 is abated. Still yet, theeffects of tents and tape lifting are also minimized.

FIG. 4 illustrates a tape drive which may be employed with the tape headsystem 300 of FIG. 3 for one embodiment of the present invention. A tapesupply cartridge 4120 and a take-up reel 4121 are provided to support atape 4122. Moreover, guides 4125 guide the tape 4122 across abidirectional tape head 4126.

A tape drive, such as that illustrated in FIG. 4, includes drivemotor(s) to drive the tape supply cartridge 4120 and the take-up reel4121 to move the tape 4122 linearly over the head 4126. The tape drivealso includes a read/write channel to transmit data to the head 4126 tobe recorded on the tape 4122 and to receive data read by the head 4126from the tape 4122. An interface is also provided for communicationbetween the tape drive and a host to send and receive the data and forcontrolling the operation of the tape drive and communicating the statusof the tape drive to the host, all as understood by those of skill inthe art.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. A method for specifying manufacture of a magnetic tape head systemhaving two individual head assemblies coupled together in opposingrelationship, each head assembly including a row bar with a headsituated therein defining a tape bearing surface which defines a tapewrap angle, the method comprising: specifying a tape wrap angle definedbetween a horizontal plane and a plane in which each tape bearingsurface resides, wherein the selected tape wrap angle is betweenapproximately 0.5 degrees and 1.3 degrees; and specifying a distancebetween end edges of the row bars to be between approximately 0.6millimeters and 0.8 millimeters.
 2. The method as recited in claim 1,further comprising specifying a length of each tape bearing surface in adirection parallel to a direction of tape travel to be betweenapproximately 0.57 millimeters and 0.7 millimeters.
 3. The method asrecited in claim 1, further comprising specifying a tape guide positionsuch that a tape approaches the head at an external wrap angle, acombination of the tape wrap angle and the external wrap angle beinggreater than the tape wrap angle.
 4. A method for manufacturing amagnetic tape head system, comprising: coupling together two individualhead assemblies in opposing relationship, each head assembly including arow bar with a head situated therein for defining a tape bearing surfacewhich defines a tape wrap angle with respect to a horizontal plane;wherein a length of the tape bearing surface and the tape wrap angle isselected such that a resolution of the magnetic tape head system issubstantially independent of a velocity of a tape, wherein the tape wrapangle is defined between a horizontal plane and a plane in which thetape bearing surface resides, wherein the tape wrap angle is betweenapproximately 0.5 degrees and 1.3 degrees, wherein a distance betweenend edges of the row bars is between approximately 0.6 millimeters and0.8 millimeters.
 5. The method as recited in claim 4, wherein the tapebearing surface length is defined as a distance between edges of thetape bearing surface.
 6. The method as recited in claim 4, wherein thelength of the tape bearing surface is substantially 0.63 millimeters. 7.The method as recited in claim 4, wherein the tape wrap angle is betweenapproximately 0.8 degrees and 0.9 degrees.
 8. The method as recited inclaim 4, further comprising setting guides such that the tape approachesthe head at an external wrap angle, a combination of the tape wrap angleand the external wrap angle being greater than the tape wrap angle. 9.The method as recited in claim 8, wherein the tape wrap angle is aboutthe same as the external wrap angle.
 10. A method for specifyingmanufacture of a magnetic tape head system having two individual headassemblies coupled together in opposing relationship each head assemblyincluding a row bar with a head situated therein defining a tape bearingsurface which defines a tape wrap angle, the method comprising:specifying a length of each tape bearing surface of the head such that aresolution of the magnetic tape head system is substantially independentof a velocity of a tape passing thereacross, wherein the length of eachtape bearing surface is between approximately 0.57 millimeters and 0.7millimeters; and specifying a tape wrap angle defined between ahorizontal plane and a plane in which the tape bearing surface resides,wherein the tape wrap angle is between approximately 0.5 degrees and 1.3degrees, wherein a distance between end edges of the row bars is betweenapproximately 0.6 millimeters and 0.8 millimeters.
 11. The method asrecited in claim 10, wherein the specified tape wrap angle is selectedsuch that a resolution of the magnetic tape head system is substantiallyindependent of a velocity of the tape.
 12. The method as recited inclaim 10, wherein the specified tape wrap angle is between approximately0.8 degrees and 0.9 degrees.
 13. The method as recited in claim 10,further comprising specifying a tape guide position such that the tapeapproaches the head at an external wrap angle, a combination of thespecified tape wrap angle and the external wrap angle being greater thanthe specified tape wrap angle. the tape bearing surface is substantially0.63 millimeters.
 14. The method as recited in claim 13, wherein thetape wrap angle is about the same as the external wrap angle.